In order to solve the global environmental problems caused by the depletion of fossil fuels and the use thereof, studies have been actively conducted on alternative energy sources, which may be regenerated and are clean, such as solar energy, wind power, and water power. Among them, interests in solar cells which change electric energy directly from the sunlight have been greatly increased. Here, the solar cell means a cell which produces current-voltage by using a photovoltaic effect of absorbing photoenergy from the sunlight to generate electrons and holes.
Organic-inorganic hybrid perovskite materials have recently drawn attention as a light absorbing material for organic-inorganic hybrid solar cells due to the characteristics in which the absorption coefficient is high and the material can be easily synthesized through a solution process.
In general, an absorbing layer used in an organic-inorganic hybrid solar cell is composed of a single cation, a metal ion, and a halogen ion as a basic structure which uses an AMX3 component, but in this case, there are problems with low efficiency and stability caused by vulnerability to moisture, and the like.
In particular, a perovskite formed of a single cation and representatively used has problems in that the stability deteriorates and the properties are changed due to lattice spacing according to a phase transition at a driving temperature or a temperature equal to or less than the driving temperature. The perovskite easily undergoes a phase transition even in a driving or typical storage state, and thus is converted into other crystals rather than perovskite, so that there is a problem in that characteristics of an inherent solar cell deteriorate or are lost.